Light conducting rod endoscopic instrument which makes use of the principle of total internal reflection to sight perpendicularly to the rod axis



J. FROIO 3,413,067 COPIC INSTRUMENT WHICH MAKES USE XE? 34139Q67 a Nov.26, 1968 LIGHT CONDUCTING ROD ENDOS OF THE PRINCIPLE OF TOTAL INTERNALREFLECTION TO SIGHT l G 6 9 m 0 r3 3 PERPENDICULARLY TO THE ROD AXIS 5Sheets-Sheet 1 Filed March 25, 1964 INVENTOR. NICHOLAS J. FROIO BYssh-330w 0Q- TN 355mm- Nov. 26, 1968 N. J. FROIO 3,413,067

LIGHT CONDUCTING ROD ENDOSCOPIC INSTRUMENT WHICH MAKES USE OF THEPRINCIPLE OF TOTAL INTERNAL REFLECTION TO SIGHT PERPENDICULARLY TO THEROD AXIS Filed March 25, 1964 3 Sheets-Sheet 2 ll 20 '26 r I04 0 ran I20INVENTOR:

' NICHOLAS J.FRO|O N. J. FROIO 3,413,067 DOSCOPIC INSTRUMENT WHICH MAKESUSE PRINCIPLE OF TOTAL INTERNAL REFLECTION TO SIGHT Nov. 26, 1968 N E DO R G N I T C U D N OE CH T m HF G0 I L PERPENDICULARLY TO THE ROD AXIS3 Sheets-Sheet 5 Filed March 25, 1964 FIG. 9

m W F W w W mm .T I, 3 W F T I w V G 5 S w 8 l A F f L w 0 O H m m W.

LIGHT CONDUCTING ROD ENDOSCOPIC INSTRU- MEN'I WHICH MAKES USE OF THEPRINCIPLE OF TOTAL INTERNAL REFLECTION TO SIGHT PERPENDICULARLY TO THEROD AXIS Nicholas J. Froio, Harvey, Ill., assignor to Froio Corporation,a corporation of Illinois Filed Mar. 25, 1964, Ser. No. 354,529 6Claims. (Cl. 356241) ABSTRACT OF THE DISCLOSURE The disclosure describesan endoscope having in one embodiment an elongated rod likelight-transmitting solid body with a concave conical face at the distalend which provides an internal convex reflecting face radially oppositea clear coaxial side face. The viewing end is enlarged to provide anannular fr-usto-coni-cal shoulder with an annular groove thereabovewhose lower planar wall provides an internal reflecting surface forcircumferentially direct ed light to increase ambient lightingtherethrough. Auxillary light means at the shoulder, a radially recessedside face, a distal end cap and cylindrical protective sheath areprovided in other embodiments The present invention, in its broadestaspect, relates to an optical system for producing a stereopanoramicimage, the image presenting a view from a central position in all radialdirections of circumferentially arranged objects, or of the visibleportions of a single surrounding or encompassing object. Morespecifically, the stereopanoramic image which is produced by the opticalsystem of the present invention is a lemniscular distortion of arectangular panoramic image, the distortion being roughly on the orderof a Mercators Projection based on conical considerations rather than onspherical, as will be further explained presently. The optical system ofthe present invention, when employed for viewing objects or portions ofan object which present themselves for viewing in three dimensions (forexample circumferentially arranged objects), will produce astereopanoramic image of such objects or portions of an object, thestereographic depth of which is equal to the depth dimensions of theobjects or portions. When viewing objects or portions of an object whichpresent themselves in only two dimensions (for example markings or othercharacteristics on the inner surface of a cylinder), the optical systemwill produce a plan opanoramic image. Whether the optical system beemployed for viewing objects that present themselves for viewing inthree dimensions, or objects that present themselves for viewing in twodimensions, the optical system remains unchanged, the images produced ineither case flowing merely from the character of the objects beingviewed.

Briefly, the optical system of the present invention em bodies anoptically transparent body which functions partially in the manner of alens, partially in the manner of a prism, and partially in the manner ofa reflecting mirror, although, strictly and technically speaking, itdoes not meet the definition of any one of these fundamental opticaldevices. Considering only the effective image-forming surfaces of theoptical system, these surfaces are three in number, namely an outercylindrical surface, an inner aflectively convex conical surface coaxialwith the cylindrical surface, and a planar viewing surface normal to thecommon axis of the cylindrical and conical surfaces and positioned inopposition to the small base of the conical surface. These three opticalsurfaces are embodied in a single optically transparent body in 'theform of a true cylinder having one planar circular end face, the othernited St j 316m end face of the cylinder being recessed on a trulyconical bias. The net optical effect of such a transparent body is theprovision of a prismatic body having a cylindrical surface of lightincidence, an internal convex reflective conical surface which receivesthe incident light and totally reflects the same, and a plane surface oflight emergence for viewing the totally reflected light emanating fromthe convex conical surface. By such a prismatic arrangement of surfaces,the aforementioned lemniscular distortion of a stereopanoramic image isattained upon viewing the light emerging from the plane surface of theoptically transparent body.

The lemniscular distortion above referred to is not an undesirable imagedistortion. On the contrary, it is a desirable one and it constitutesone of the principal features of the present invention in that itpresents the entire stere-= opanoramic image in a small circular viewingarea directly in the line of vision of the viewer, the size of theviewing area being no greater than the area of the large base of theconical reflecting surface. Furthermore, the entire 360 field of view,which is represented by the height of the cylindrical surface ofincidence, and which is a function of the surface area of the cylinder,is, by reason of this lemniscular distortion, reduced to such a sizethat the image thereof falls wholly within the small circular viewingarea. Finally, advantage is taken of this lemniscular distortion of thepanoramic image for novel and convenient surface marking of theoptically transparent body to the end that image measurements may bemade and readings obtained which are indicative of such things as objectsize, specific object dimensions, and relative positioning of objectswith respect to one another, as well as to the optical system itself.Although image distortion involves an over-all object-to-image sizereduction, the optical system is such that by relative movement of thesystem bodily with respect to the object or objects under going viewing,any selected visible portion of an object may be brought undersurveillance and the image thereof viewed at an image magnitude which isno less than the full magnitude of the portion thus selected.

According to the present invention, a wide variety of environmentalaspects for the basic optical system briefly outlined above arecontemplated, but in all of them, and without exception, the systemremains unchanged. However, various auxilliary features may beincorporated in the optical system to enhance the efficiency thereof as,for example, the provision of a viewing extension in the form of atransilluminating rod, which may either be separate from or integralwith the prism-like transparent body, and which operates upon theprinciple of internal reflection from the side walls thereof forconducting light from the stereo or planar image to a remote point forvisualization thereof. Another auxilliary feature which may beincorporated with the basic optical system of the present invention is anovel means for applying artificial external light to and conducting thesame through the optical system for object and, consequently,image-illumination and subsequent reflection of the image light towardthe eye of the observer. An additional and mechanical adjunct to theoptical system resides in the provision of a combined protective sheathand guide for the transilluminating rod portion when the latter isincorporated in the system and which normally, when the system is not inuse, serves as a protective shield for the cylindrical and conicaloptical surfaces but which, when the system is in use, affords a. guidefor the transilluminating rod so that the position of the variousoptical surfaces may be shifted bodily as a unit with respect to theobject or objects undergoing viewing for various purposes such as objectselection, object size comparison, object size or dimensiondetermination, or image position shifting when desired.

The optical system of the present invention, and as briefly describedabove, has been designed for use primarily in connection with depth.probing operations and, toward this end, the system is embodied at oneterminal end of a cylindrical transilluminating rod, as described above,preferably as an integral portion of the rod. More aptly, thetransilluminating rod may be described as an. integral extension of theoptical system which is comprised of a. body of optically transparentmaterial having the aforementioned cylindrical surface of lightincidence and the convex conical reflecting surface associatedtherewith. The integral body, thus constructed, is generally in the formof a conventional endoscope and which may be inserted into a bore orother cavity for lateral viewing purposes simultaneously in all radialdirections. When. so constructed, the resultant device may be founduseful as a. bore inspection instrument useful, for example, inconnection with inspection of the inside cylindrical bores of valve orpump casings in order to ascertain the nature of the surface finishthereof, or to detect the presence of flaws or other defects, in whichcase the resultant circular lemniscular image produced will present.itself as a. planar two dimensional image, or the inspection of anintersecting radial bore, in which case a stereo or three dimensonalimage will be produced. Such a device may also find medical or surgicaluses for examining or observing the functions involved in connectionwith human or animal body cavities; for example, as a bronchoscope or alaryngoscope. When thus used in the manner of an endoscope, the deviceis not limited to optical viewing of the image which is produced by theoptical system associated there-- with inasmuch as it is contemplatedthat the optical system may be employed for photographic exposurepurposes or for the transmission of certain types of electron beams.Irrespective however of the particular use to which the presentinvention may be put, the essential features thereof are at all timespreserved.

The provision of a novel optical system and its incorporation in anendoscopic type of instrument or device as set forth above being theprincipal object of the invention, it is a further object to providesuch a device wherein the transparent body which provides the opticalsystem may be formed of a transparent or optically clear plasticmaterial such as Lucite, and which, moreover, may be machined as anintegral unit from cylindrical rod stock, thereby contributing towardeconomy of manufacture.

The provision of a depth probe inspection device which can be devoid ofmoving arts and in which the optical surfaces of light incidence,reflection and emergence are permanently fixed with respect to oneanother so that the system cannot get out of proper focus orcollamination; one which oherwise is rugged and durable and therefore isunlikely to get out of order; one which by reason of such ruggedness isable to withstand comparatively rough usage; one which is of compactdesign and of small proportions so that it may conveniently betransported on the person of the physician, surgeon, mechanic, inspectoror other user; one which has a shape characteristic which is conducivetoward ease of manipulation; and one which, otherwise, is well adaptedto perform the services required of it, are further desirable featureswhich have been borne in mind in the production and development of thepresent invention.

Numerous other objects and advantages of the invention, not at this timeenumerated, will readily suggest themselves as the following descriptionensues, and, although for the sake of convenience and quickapprenhension of the invention the invention is sometimes described anddefined herein in connection with vertical and horizontal orientations,it is to be noted that the invention contemplates use in allorientations as required Without limitation with respect to anyparticular one.

In the accompanying three sheets of drawings forming a part of thisspecification, several illustrative embodiments of the invention havebeen shown.

In these drawings FIG. I is a perspective view of a depth probing deviceor endoscope constructed according to the principles of the presentinvention and embodying the novel optical system thereof;

FIG. 2 is a sectional view taken substantially centrally andlongitudinally through the device of FIG. 1 and showing the sameoperatively installed in a bore forsurfaee inspection purposes;

FIG. 3 is an end view of the device of FIG. 1;

FIG. 4 is a fragmentary sectional view taken substantially centrally andlongitudinally through the upper region of the device of FIG. 1 andillustrating the manner in which an external source of artificial lightmay be applied thereto, the view representing a modified form of theinvention;

FIG. 5 is a sectional view taken substantially along the line 55 of FIG.4 in the direction indicated by the arrows;

FIG. 6 is a perspective view, similar to FIG. 1 showing a slightlymodified form of depth probing device or endoscope embodying the opticalsystem of the invention;

FIG. 7 is a sectional view similar to FIG. 2 showing a further modifiedform of depth probing device or endoscope together with a retractibleprotective shield for the optical system of the device, the device beingoperatively insertable in a bore with the optical system thereof inretracted and protected position;

FIG. 8 is a fragmentary sectional view of the depth probing device ofFIG. 7, showing the optical system projected into its operative positionpreparatory to inspection of an intersecting bore;

FIG. 9 is a panoramic chart of a cylindrical light incident surfaceemployed in connection with the form of endoscope shown in FIG. 6 andillustrating certain reference graduations associated therewith;

FIG. 10 is a composite diagram representing the field of view of theendoscope of FIG. 6, no image being present, and illustrating thecomposite optical effect of the reference graduations;

FIG. 11 is a fragmentary panoramic chart of the inside cylindricalsurface of a large diameter bore having a plurality of defects therein,and showing the intersection of such bore with a small diameter bore,the two bores being within the field of view of the optical system ofthe endoscope of FIG. 6;

FIG. 12 is a composite diagram of the visible image represented by thefield of view shown in FIG. 11 and as viewed through the endoscope ofFIG. 6;

FIG. 13 is a fragmentary composite diagram similar to FIG. 12, showingthe effect of a shift of the optical system bodily to a position whereinone of the defects being examined is brought into collamination withcertain of the reference graduations for size and symmetrydetermination; and

FIG. 14 is a perspective view, schematic in its representation,illustrating the basic optical system of the present invention.

Referring now to the drawings in detail and in par ticular to FIG. 14wherein the basic optical system which underlies the various forms ofthe invention illustrated herein has been portrayed, this system ispredicated upon the provision of a solid prism-like or prismatic body ofoptically clear material such as optical glass or a suitable plasticmaterial such as Lucite. Such a body has been designated in its entiretyat 20. The body 20 is of cylindrical design and is smooth and polishedon all surfaces thereof. The body 20 is provided with a cylindrical sideface 22, an upper planar circular end face 24, and a lower or underneathconcave conical end face 26 having a slant angle of 45 and the verticalaxis of which is equal in height to the height of the side face 22 sothat the apex 27 of the cone lies on and at the center of the end face24. The lower concave conical end face 26 establishes an effectivelyconvex internal optical face 28 (see also FIGS. 1 and 2) within thetransparent body itself. The three faces 22, 24 and 28 of the body 20cooperate optically with one another to provide a compound lens-prismcombination wherein the faces 22 and 24 function in the manner of lensesand the internal face 28 functions in the manner of a totally reflectingprism involving internal reflection. Because the body 20 does notpossess two planar faces it cannot be defined as a prism, and because itaffords neither light convergence nor divergence, it does not fit theordinary definition of a lens. Suffice it then, for purposes ofdiscussion herein and for purposes of claim terminology subsequently, torefer to this body 20 as an effectively prismatic or prism-like body.

The prismatic body 20 embodies the entire basic optical system of thepresent invention and, in the use thereof, it is positioned centrally ofa series of circumferentia lly arranged objects 0 and O and coaxially ofthe series. The cylindrical side face 22 thus constitutes a surface oflight incidence as indicated by the horizontal arrows in FIGS. 8 and 14.The light issuing from the circumferen tially arranged objects such asthe two exemplary objects 0 and 0 passes radially inwardly of the sideface 22 and, since the angle of entry is truly radial or normal to thesurface of the cylindrical face 22, there is no deflection in thedirection of the light rays as they enter the body 20 regardless of theindex of refraction of the material involved. The radial inwardlydirected rays, after entering the body 20 through the cylindrical sideface 22, then are reflected upwardly from the internal convex conicalface 28 due to the phenomenon of total internal reflection as indicatedby the vertical arrows. The end face 24 constitutes a surface of lightemergence and it is this surface which is viewed by the eye E of theobserver from a central point above the surface. The resultant compositeimage which is seen by the observer 'will be of a circular nature, thiscomposite image being schematically represented by the dotted circlelabelled 1. The individual images I and I appearing within thiscomposite image I will be distorted, the distortion being of alemniscular nature due to well known phenomenon which is attendant uponthe reflection of light from a convex conical mirror wherein objectwidth is reduced and object height remains the same. The composite image1 and the individual images I and I associated therewith are virtual,inverted and reduced, as is the case in connection with all concavemirrors or reflecting surfaces, whether the same be spherical, conicalor cylindrical. Thus, these images which are in the form of individuallemniscates appear to lie well below the large base of the conicalsurface 26. The reduction of images is not regular. Actually it takesplace progressively and radially inwardly of the composite image, therebeing no reduction in size at the extreme periphery of the image and thereduction amounting to 100% at the center of the image. Circular objectssuch as the objects 0 and 0 thus will take on the tear drop imageconfiguration shown at I and I In a general way, this type of imagereduction is similar to a Mercators Projection wherein distances at thepoles of the earths sphere are magnified with respect to distances atthe equator.

The optical system described in connection with the prismatic body 20 ofFIG. 14 has been embodied in a practical optical instrument in the formof an endoscope the details of which are disclosed in FIG. 1. In thisembodiment of the invention, the optical system of FIG. 14 has beenincorporated bodily and without change in the lower end region of anelongated cylindrical transilluminating rod 32. The transparentprismatic body 20 with its cylindrical polished side face 24, itsconcave conical end face 26, and its internal effective convex opticalface 28, occupies a position at the extreme lower end region of theelongated transilluminating rod and is integral and coaxial therewith.Actually, in the manufacture of the endoscope 30, the rod 32 and body 20are machined from a single length of Lucite or other optical rod stockcapable of being machined and thus the end face 24 of the schematicallyillustrated optical system of FIG. 14 exists only as an imaginary one inthe transverse juncture plane between the transilluminating rod 32 andthe body 20. This juncture plane is the transverse plane which passesthrough the apex 27 of the internal conical face 26 normal to the axisof the cone. The transparent cylindrical body 20 and the elongatedcylindrical transilluminating rod 32, being integrally formed, provide,in effect, a single elongated optical body which has been designated inits entirety at 34. On such a basis, the 'body 34 may be regarded asbeing comprised of a prismatic body portion 20 and a transilluminatingrod portion 32. For convenience of description and claim definition,this terminology will be adhered to hereinafter.

Still referring to FIG. 1, the outer cylindrical surface of thetransilluminating rod portion 32 of the body 34 is preferably, but notnecessarily, rendered translucent by a suitable etching, sanding, orother process, while the cylindrical face 22 of the prismatic bodyportion 20 thereof is polished and therefore clear.

The upper end region of the generally cylindrical body 34 is providedwith an enlarged head portion '36 of slightly larger diameter than thediameter of the rod portion 32, this head portion defining a downwardlyand outwardly directed frusto-conical shoulder 38. The outer cylindricalsurface of the head portion 36, as well as the frusto-conical shoulder38, are optically clear for the purpose that will be describedpresently. The lower region ."of the head portion 36 is formed with arelatively deep, narrow annular groove 40 therearound, the function ofwhich likewise will appear presently. As shown in dotted lines in FIG.1, the bottom wall 42 of the groove 40 presents a narrow cylindricalband-like surface the diameter of which is somewhat less than thediameter of the rod portion 32 of the body 34.

Considering now the previously described optical systern which isafforded 'by the prismatic body portion 20, as integrally embodied inthe optical body 34, it will be apparent that the transilluminating rodportion 32 and the enlarged head portion 36 function, in effect, todisplace the normal planar circular optical light-incident surface 24(FIG. 14) an appreciable distance upwards from its normal position ofFIG. 14 and thus establish an elevated light-incident surface 44(FIG. 1) for viewing purposes by the eye of the observer. This elevatedoptical surface 44 is slightly larger in diameter than the normalviewing surface 24 of the optical system as portrayed in FIG. 14, but,despite this, the basic optical system remains substantially the same inoptical function. The transilluminating rod portion 32 has no effect onthe image which is established by the optical system, either as toregards its size or its shape characteristics, the only function of thisrod portion being to collect and transmit the reflected light issuingfrom the internal conical face 28 directly to the eye of the viewer.This rod portion 32 also serves the incidental function of maintainingthe eye of the observer at a greater distance from the image than whenthis rod portion is not present. The length of the transilluminating rodportion 32 may be varied within wide limit-s ranging from an extremelyshort length to the maximum length which is within the capabilities ofthe observer in viewing the image. Ordinarily, this length will bedetermined by the effective depth of the cavity to be explored by theendoscope instrument.

Referring now, additionally, to FIG. 2 wherein the optical instrument orendoscope 30 of FIG. 1 is illustrated for exemplary purposes as beingoperatively installed in a bore 50 the surface characteristics of whichit is desired to explore, the entire internal surface of the bore may beexplored by a progressive shifting of the instrument vertically withinthe bore to bring the prismatic body portion 20 into radial registerwith selected portions of the bore. A seating ring 52 may surround therod portion 32 of the body 34 if desired to assimilate the downwardthrust of a split supporting band or collar 54 which may be tightenedupon the instrument at various selected longitudinal regions by means ofa thumb screw 56.

Assuming that a selected cylindrical region such as the regiondesignated at 58 in FIG. 2 is to be examined for surface finish orsurface defects, the body portion 20, together with the adjacent regionof the transillu minating rod portion 32 will be telescopically insertedinto the bore and lowered until the body portion 20 is in radialregister with the portion 58 to be examined. Thereafter the thumb screw56 may be tightened to maintain the instrument in a fixed position.

Illumination of the selected region 58 of the bore 50 will automaticallybe effected by reason of ambient light conditions in the vicinity of theinstrument 30 exteriorly of the bore 50. Parallel side transilluminatingrods are well known, as are the principles of light transmission andlight emission associated therewith, and therefore a detailed discussionof these principles will not be set forth herein, suffice it to say thatlight which enters one end face of an optically clear transilluminatingrod will travel, substantially undiminished in intensity to the otherend face and pass outwardly of the latter with practically nodistortion. Thus, an object presented to one end face of the rod willpresent to the eye of the viewer at the other end face a substantiallyundistorted erect image of such object. This ability to transmitundistorted images of undiminished light intensity is predicated uponwell known phenomena relating to total internal reflection in prismaticbodies. It is well known that total reflection will occur at the boundryseparating two media having different refractive indices when any ray inthe medium of higher index is directed toward the other medium at anangle of incidence greater than the critical angle. Thus, in a parallelside rod, light which enters the rod through one end face thereof and isdirected longitudinally along the rod is confined within the cylindricalcontour of the rod substantially in its entirety since at no time doesit approach the surrounding medium at an angle less than the criticalangle. An extremely small amount of diffused light may escape later allythrough the outer cylindrical face of the rod due to microscopicparticle impurities in the optical media of the rod but the amountinvolved is negligible and does not detract appreciably from thequantity of light issuing from the end face of light emergence. An imageexisting by reason of such emerging light remains substantiallyundiminished in intensity.

By these tokens, ambient light which enters the viewing'end face 44- ofthe optical body 34 will pass through the circular opening afforded bythe bottom wall 42 (FIG. 1) of the annular groove 40 and passlongitudinally along the rod portion 32 to the internal reflectiveconical face 28 of the prismatic body portion 20. Some light will enterthe body 34 radially inwardly through the cylindrical side surface ofthe optically clear enlarged head portion 36. An additional andappreciable amount of light will pass inwardly through the opticallyclear frusto-conical shoulder 38 and impinge against the lower side wall60 (FIG. 2) of the annular groove 40, from whence it will be totallyreflected by total internal prismatic reflection and directedlongitudinally along the rod portion 32 to the internal conicalreflecting face 28. Still more light will pass radially inwardly indiffused form through the translucent cylindrical side surface of therod portion 32 of the body 34. The net result of all of this lightentering the body 34 at various locations or regions thereof will be toflood the interior of the body, so to speak, with light rays. Theselight rays, which ordinarily in connection with conventionaltransilluminating rods would emerge longitudinally from the lower endface of the rod, are in the present instance prevented from thusemerging due to the total reflecting function. of the internal opticalconical face 28 which is presented. to these light rays at an angle lessthan the critical angle of incidence The light rays therefore will bereflected radially outwardly of the optical body 24 in all radialdirections for illumination of the surrounding object which, in thepresent instance, is the selected limited portion 58 of the internalbore 50. The thus illuminated. object, i.e., the area 58 of the bore 50,is then visible as a lemniseular distortion of the image panorama to theeye of an observer looking through the circular end face 44, by reasonof the reflection. phenomena associated with total reflection of lightfrom a conical surface as previously described in connection with thebasic optical system of FIG. 14.

Under certain circumstances it may be found desirable to illuminate thebore or other object undergoing visual exploration with artificial lightand one means for accomplishing this has been illustrated in FIGS. 4 and5. Illumination is accomplished without modifying the basic opticalsystem described in connection with FIG. 14, or the embodiment thereofin the endoscope instrument of FIGS. 1 and 2. Accordingly, a torus-likeannular casing 70 surrounds the upper end region of thetransilluminating rod portion 32 immediately below the level of thefrustoconical shoulder 38 and may either be frictionally held inposition therearound or cemented to the rod portion 32. The casing 70 issquare in radial cross section and has operatively mounted therein aseries of circumferentially spaced light-emitting elements 72 in theform of incandescent filaments adapted to "be electrically connected toa suitable source of energizing current (not shown). The

innermost upper annular peripheral edge of the casing 70 is truncated asat 74 to provide an exit window for light rays emanating from theelements 72, the window being in coextensive register with and closeproximity to the transparent frusto-conical surface 38 as shOWn in FIG.4. Artificial light rays entering the body 34 through the transparentfrusto-conical surface 38 will assist in flooding the interior of thebody 34 with light as previously described, but, specifically,directional rays emanating from the filaments 72 will enter the body 34through the frusto-conical surface 38 and strike the lower side wall 60(FIG. 2) of the annular groove 40 and thus be reflected generallydownwardly as indicated by the arrows in FIG. 4 and, thereafter, bytotal internal reflection from the cylindrical side wall of thetransilluminating rod portion 32, ultimately be directed to the internalconical reflecting surface 28.

In order to shield the eye of the observer from light rays issuing fromthe filaments of the light sources 72, a suit able filler material orstrip 76 may be positioned within the annular groove 40. This strip isof an opaque nature and its function is principally a shielding onerather than a reflecting one. However, if desired, the strip, inaddition to being opaque, may be of a reflecting character to preventany rays which may be directed toward the surface at an angle greaterthan the critical angle from entering the head portion 36 through thesurface 60. In such an event, the filler strip 76 may be formed fromaluminum or other reflective metal foil.

In FIG. 6, a modified form of endoscope instrument 130 has beenillustrated, the instrument embodying the basic optical system of FIG.14. The optical body 134 which, in its entirety, comprises theinstrument is identical in many respects to the optical body 34 of theform of instrument described in connection with FIG. 1 and therefore, inorder to avoid needless repetition of description, correspondingreference numerals but of a higher order have been applied to thecorresponding parts as between the disclosures of FIGS. 1 and 6respectively.

The shape characteristics of the optical bodies 34 and 134 of FIGS. 1and 6, respectively, are substantially identical except for a slightreduction in the diameter of. the cylindrical body portion as indicatedat 121.

An additional difference resides in truncation of the con-= cave conicalend face 26 of the body portion 20 and consequent truncation of theeffective internal reflecting conical optical surface 128 (see FIG. 7),thus providing a corresponding frusto-conicalend face 126 and aninternal reflecting frusto-conical face 128 in the body 134. A thirddifference resides in the elimination of the frustoconicallight-incident shoulder 38 and the substitution therefore of a radialshoulder 138. Truncation of the internal and external faces 128 and 126,respectively, is effected by the provision of a coaxial pilot bore 129(see FIG. 6) in the lower end face of the body portion 120 and whichintersects the cone outline of the surface 126.

Truncation of the internal optical surface 128 has little effect on thecharacter'of the images which are produced for visualization when theinstrument is in use inasmuch as the portion of the cone which isremoved is merely a small fragment of the apex region of the cone. Thisapex region, when considered in connection with the internal conicalface 128 of FIG. 1 is productive of an image fragment which is ofgreatly reduced size and, furthermore, it is possible, by propermanipulation of the instrument, to maintain the entire image within theconfines afforded by the frusto-conical face' 128 for all useful boreinspection, comparison or measurement purposes as made clear presently.

In addition to the above-described variations in shape characteristicsof the optical body 132 over the body 32, the transparent opticalsurfaces represented by the upper end face 144 of the head portion 136and the side face 124 of the optical body portion 120 are provided withsurface markings which, when imposed upon the optical system and viewedby the eye of the observer, provide convenient reference lines by meansof which image dimensions, image positioning, and image shapes mayconveniently be ascertained. The surface markings selected herein forillustrative purposes are purely exemplary and it will be understoodthat other surface markings than those shown may be employed if desired.

The surface markings on the upper end face 144 are in the form of aseries of concentric circles 181 these circles being three in number.While three such circles have been illustrated herein, a greater orlesser number may be employed. The three circles are concentric with thecircular end face 14.4. The surface markings on the cylindrical sideface of the optical body portion 120 are in the form of a first seriesof three vertically spaced parallel band-like lines 183, a second seriesof three spaced vertical and longitudinally extending lines 185, and asingle vertical longitudinally extending reference line 187. All ofthese reference lines are visible in sharp focus when yiewed by the eyeof the observer and a superimposed pattern of lines such as has'beenillustrated in FIG. constitutes the composite pattern image whichis'seen by the eye.

The circular reference lines of the series 181 are not used as a patternchart in connection with image measurements although their patter-nlines are superimposed over the image which is viewed by the eye. Thesereference lines are close to the viewing eye and therefore theirapparent thickness will prevent them from useful register with smallportions of the image and they should not be used for measuring. Thepurpose of the reference lines is solely to facilitate eye alignmentwith the axis of the instrument for themost effective viewing of theimage.

The vertical reference lines of the series 185 have been labelled w1, w2and w3 respectively, as have their pattern representations in the chartsof FIGS. 10, 12 and 13. These lines, .when imposed over a given image,may be employed to facilitate a determination of the width of an objectsuch as a flaw or other small defect.

The vertical line 187 has been labelled r, as has its patternrepresentation in the various charts, and this line, iii combinationwith the vertical lines w1, w2 and w3, may be employed for facilitatinga determination of the circumfer'ential distances around the area of thebore which wiil be is undergoing inspection. Such distances may bespacings between circumferentially arranged objects, or they may berelatively large flaw width dimensions. When considered in connectionwith the reference lines w1, w2 and w3, distance measurements such ashave been indicated at d1, d2 and 03 in FIG. 9 are available for use inascertaining circumferential distances.

The vertically spaced band-like lines of the series 183 have beenlabelled h1, h2 and h3 respectively. These lines serve to facilitatealdetermination of vertical spacings or small vertical heights ordistances associated with an object such as a flaw within the boreundergoing inspection. The functions of the various reference linesdescribed above and the relationship which they bear to another inestablishing a reference pattern for superimposition over a given imageor series of images may best be understood by graphically illustratingthe distortion pattern which result from the optical viewing ofspecificshapes, utilizing the endoscope instrument of FIG. 6. FIG. 9 isa chart which represents a panoramic view of the cylindrical opticalface of the body portions 20 and 120, the cylinder being unfolded to aplanar condition. The chart shows the various reference lines with noimage superimposition thereon. FIG. 10 is a diagram representing theimage of the various reference lines as viewed by the eye when there isno object present to be viewed. FIG. 11 is a chart showing a limitedportion of the field of View when viewing five differently shapedobjects with the adjacent reference lines superimposed thereover. FIG.12 is a diagram of the actual field of view as seen through theendoscope instrument when viewing the five objects of FIG. 11 and thepositional relationship of the various reference lines with respect tothese objects.

It is a demonstrable fact that if an object and a reflective cone arepositioned on a horizontal planar surface in side-by-side relationship,the reflected image of the object will be distorted in cochleatefashion, the upper regions of the image being progressively reduced insize. Thus a cube will yield the image of a pyramid, while a cylinderwill yield the image of a cone. The reduction in size is effectivethrough the entire height of the image except for its base which remainsequal in size to the size of the base of the object. This reduction insize is effective only insofar as the width of the image is concerned.The height of the image at all times remains the same as the height ofthe object. If the reflective cone is elevated slightly above the levelof the object, the lower portion of the image will run off the lowercircular edge of the cone, so to speak, while the upper region of theimage will increase in width. If the cone is lowered with respect to theobject, a portion of the diminished upper region of the image willshrink to a point and run off theapex of the cone. This phenomenon ofreflective conical surfaces is carried into the optical system of thepresent invention in such a manner that radial directions of the viewedpanoramic image represent object height and do not diminish in sizeregardless of relative vertical displacement between the conicalreflective surface 128 (FIG. 6) and the object, while circumferentialdirection of the circular panoramic image represents object width.

Bearing these considerations in mind, and assuming for purposes ofdiscussion that the circle appearing in the chart fo FIG. 11 representsthe intersection of a small bore such as the bore of FIGS. 7 and 8 witha larger bore 102 within which the endoscope instrument 134 is insertedfor the purpose of inspecting the bore 100, the image which the bore 100will present to the eye is the teardrop configuration in FIG. 12. Noradial diminution has taken place but appreciable width diminution hasoccurred. To test the bore for ,concentricity, the teardrop shape willbe broughtinto centered relationship within the intersecting confines oftherefer 'ence lines W1, W3, hl and k3 insofar-as is possible bymanipulation of the instrument bodily as a whole within the bore 102.Rotation of the instrument about its longitudinal axis will sweep theradial reference image lines W1, W2, w3 and r around the field of viewfor image centering purposes, While raising or lowering of theinstrument bodily will draw the image radially inwardly or radiallyoutwardly to decrease its width and bring the same into the desiredposition of register with the various reference lines. With the teardropimage thus in tangential relationship to the four reference lines w1,w3, I11 and 123, and with the line w2 bisecting the teardrop image, itmay be assumed that the object is truly circular. The presence of a protruding burr or other imperfection such as has been indicated at 104 inFIG. 7, even though the flaw be remote from the region of boreintersection, will be revealed in the image by a projection such as hasbeen shown at 106 within the confines of the circles of FIG. 11.

Experimentation has shown that a square object pattern, an invertedtriangular object pattern, and upright triangular object pattern and anelongated vertically disposed narrow rectangular object pattern such ashave been illustrated in FIG. 11, will assume the shield shape imagepattern, the distorted triangle image pattern, the trapezoidal imagepattern, and the knife blade image pattern respectively of FIG. 12.

In FIG. 13, the image pattern illustrated shows the effect which isproduced on the various images of FIG. 12 when the square object patternof FIG. 11 is brought into register with the intersecting referencelines w2 and I12 and is centered between the lines w, w3, h] and 113.The trapezoidal image pattern of FIG. 12 has increased in width but.remains the same in length; the narrow rectangular image pattern hasbecome wider; the relatively sharp pointed end of the teardrop imagepattern of FIG. 12 has become blunt and appreciably enlarged in widthwith a portion of the image pattern having moved from the field of view,while the two triangular image patterns have moved from the field ofview. Such. image displacements are caused by raising the endoscopeinstrument bodily in the bore 102 and rotating the same through a smallangle to effect the necessary image and reference line register.

From the above description it will be understood that an operator, aftera short period of study and experimentation withthe conversion ofvarious object shapes or markings will become skilled in imagedetermination so that by viewing a given image shape, he may readilyvisualize the particular shape of the object from which the image isderived. By thus acquiring skill in image determination, an operatorsuch as a surgeon or an engineer may become proficient in bore orpassage examination utilizing the endoscope instrument of the presentinvention.

In FIG. 7, the endoscope instrument of FIG. 6 is shown as being equippedwith an articulate protective sheath 200 for the optical body portion120 and a portion of the transilluminating rod portion 132. An end capor plug 202 also is provided for protecting the polished concavefrusto-conical surface 126. The sheath 200 is of open-ended cylindricaldesign and it is telescopically received over the rod portion 132. Theend cap or plug 202 is in the form of a circular closure disk whichextends across and closes the cavity afforded by the provision of thefrusto-conical surface 126 in the prismatic body portion 120 of theelongated body portion 134. A pilot plug or stem 204 is formed centrallyof the end cap and projects into the pilot hole 129 and is cemented inposition therein. The peripheral region of the end cap 202 overhangs thecylindrical confines of the rod portion 132 and is recessed as at 206 toprovide a seat for the lower open rim of the tubular sheath 200. Thesheath 200 is normally maintained in its seated relationship on the endcap 202 by means of a spring 208 which surrounds the rod portion 132 andbears at its lower end against an annular outwardly turned flange 210provided at the upper rim of the sheath, and. at. its upper end againstthe downwardly facing shoulder 138 at the juncture region between thehead portion 136 and rod portion 132. When seated on the end cap 102,the prismatic body portion 120 is completely withdrawn into the sheathand consequently the polished optical side face 124 thereof is protectedfrom contact with external objects, as well as being shielded fromcontamination by dirt or moisture.

The prismatic body portion 120 is adapted to be projected outwardlybeyond the lower open rim of the sheath 200 inv order to expose the samefor operative bore inspection purposes in a manner that will be madeclear presently, the exposed position of the body portion beingillustrated in FIG. 8.

In actual use for bore inspecting purposes, the cylindrical sheath 200is inserted endwise into a bore such as the bore 102 and is lowered tothe desired depth within the bore. In the exemplary use of the endoscopeinstrument 134 shown in FIG. 7 wherein it is desired to ascertain thecharacter of an intersecting bore such as the small bore 100, the sheathwill be lowered to such an extent that the open lower rim thereof justmeets the bore intersection. Thereafter the previously mentioned seatingring 52 and split locking collar 54 are applied to the sheath 200 toprevent further downward movement thereof. With the sheath 200 thus inposition, downward pressure is applied to the optical body 134 againstthe yielding action of the spring 208, thus lowering the prismatic bodyportion into register with the intersecting bore as shown in FIG. 8 andestablishing the previously described object outline represented by thecircle of FIG. 11. Light entering the optically clear body of theinstrument as previously de scribed is transmitted to the interior ofthe bore 100 so as to illuminate the same and produce the imageschematically represented by the teardrop image pattern of FIG. 12 aslikewise previously described. The bore imperfection 104 will then bevisible as the image representation 106 within the teardrop outline.After the necessary bore inspection has been completed, pressure on theinstrument may be released and the spring 208 will restore the prismaticbody portion to its retracted position within the sheath 200 and withthe end cap 202 closing the lower open rim of the latter. It is to benoted at this point that the reduced diameter of the body portion 120affords a clearance region or annulus between the side surface 124 andthe tubular sheath 200 to prevent abrasion of the polished side surfaceduring relative sliding movement between the sheath 200 and body 134.

The invention is not to be limited to the exact arrange ment of parts orto the specific shape characteristics of the optical bodies 34 and 134shown in the accompanying drawings and described in this specificationas various changes in the details of construction may be reorted towithout departing from the spirit of the invention. For example, thevarious graduation lines which have been illustrated herein as beingapplied to the optical faces 124 and 144 in the form of the inventionshown in FIG. 6 may be applied to the optical faces 24 and 44 in theform of the invention shown in FIG. 1. Furthermore, these referencelines are purely exemplary of one system of reference marking. Othersystems involving a greater or lesser number of such lines, or lineswhich extend in directions other than vertically and circumferentiallyare contemplated. The diameters of the various body sections may bevaried to accommodate different size bores or passages to be inspected,while the length of the transilluminating rod sections 32 and 132 may bevaried for different depth explorations. Although the bodies 34 and 134are shown and described herein as being of one-piece integralconstruction, it is within the purview of the invention to construct thesame in plural sections operatively cemented together by a transparentbonding agent. In such an in" stance it is preferable that all of thesections, as well as the bonding agent, be formed of materials havingidentical indices of refraction. It is not essential however, that such.be the case because the phenomenon of refraction establishes an opticaloffset which merely displaces the image slightly but does not distortthe image, Finally, although the transilluminating rod portions 32 and132 of the two forms of optical-bodies 34 and 134 respectivelyillustrated herein have been described as being formed of effectivelyrigid cylindrical rod stock incapable when out in relatively shortlengths of being flexed, it is within the purview of the invention toform the optical bodies of optically clear plastic or other materialswhich will yield when flexing stresses are applied thereto. Certain ofthe phenol formaldehyde resinous condensation products are extremelyflexible at room temperatures when formed into rod stock at diameters onthe order of one-quarter inch and less and when such rods are employedas the basis for forming the optical bodies 34 and 134 they may becaused to follow the tortuous contours of irregular bores the interiorsof which are to be inspected. In such instances the panoramic imagesproduced will present no distortion other than the herein describedlemniscular distortion which is inherent in the optical system of thebody 20 of FIG. 1.

Having thus described the invention and several embodiments thereof andthe results and advantages attained thereby, it will be apparent tothose skilled in the art how the stated objects are accomplished and howvarious and further modifications can be made therein without departingfrom the spirit of the invention the scope of which is commensurate withthe appended claims,

What is claimed is:

1. An endoscopic instrument for making examinations within a bodycavity, said instrument comprising an elongated solid cylindrical rod ofoptically clear material and having a proximate viewing end with anenlarged cylindrical head portion coaxial with the rod, and a distalexploratory end region adapted for insertion into the cavity, the endface of said rod at the proximate viewing end thereof being planar andextending transversely of the rod, said head portion being formed withan external annular groove therearound having a band-like bottom walland opposed planar side walls, the end face of said rod in the distalend region being provided with a concave conical socket-like depressiontherein establishing within the rod at the extreme distal end thereof aninternal ettective convex conical reflecting surface which is coaxialwith the rod, the juncture region between said enlarged head portion andthe remainder of the rod establishing an annular frusto-conical lighttransmitting surface for entry of ambient light into said enlarged headportion, the side wall of said annular groove remote from said planarend face establishing an internal reflecting face for total reflectionof light entering the enlarged head portion through said frusto-conicallight transmitting surface and direction of such light longitudinally ofthe rod toward the distal end thereof, the portion of the cylindricalside face of the rod which is in radial register with said effectiveconvex conical reflecting surface constituting a surface of light transmission whereby light reflected from the wall of the body cavity andentering the body through said portion of the side face of thecylindrical rod will be totally reflected from said eflective convexconical reflecting surface towards the proximate end of the rod andemerge from. said planar end face,

2. An endoscopic instrument as set forth in claim 1 and including,additionally, a torus-like annular casing surrounding said rodimmediately below said frusto-conical light-transmitting surface, and aseries of light-emitting elements operatively disposed within saidcasing in circum ferentially spaced relationship therearound, saidcasing being formed with an annular light transmitting opening thereinin register with said frusto-conical surface,

3. An endoscopic instrument as set forth in claim 2 and including,additionally, an opaque filler material dis= posed within said annulargroove for shielding said trans verse planar end face from extraneouslight emanating from the vicinity of said groove,

4. An endoscopic instrument for making examinations within a bodycavity, said instrument comprising an elongated generally cylindricalrod having an enlarged cylindrical head portion at its proximate viewingend, acyl1ndrical prismatic body portion at its exploratory end, and anintermediate transilluminating cylindrical rod portion, said headportion prismatic body portion and intermediate transilluminating rodportion being disposed in coaxial end-to-end relationship, said headportion presenting a planar transverse end face for viewing purposes,said prismatic body portion presenting a cylindrical side face and aconcave conical end face establishing within the prismatic body portionan effective internal convex reflecting conical face in radial registerwith said side face, said apex region of said concave conical end faceis truncated by the provision of a cylindrical pilot socket centrally ofsaid end face whereby the effective internal convex reflecting conicalface likewise is similarly truncated, a circular end cap extendingacross the open base of said concave conical end face, said end capbeing formed with a central pilot stem projecting into said pilot socketand secured therein, said side face of the prismatic body constituting asurface of light incidence whereby light reflected from the wall of thebody cavity and entering the prismatic body through said side face willbe totally reflected from said effective convex conical reflectingsurface and directed through the intermediate transilluminating rodportion to the planar end face of the enlarged head portion foremergence therefrom.

5. An endoscopic instrument as set forth in claim 4 wherein the junctureregion between said enlarged head portion and the transilluminating rodportion establishes a frusto-conical light transmitting surface forentry of ambient light into the enlarged head portion, and meansinternally of said head portion for reflecting light entering the headportion through said frusto-conical light incident surface toward saidinternal convex reflecting surface.

6. An endoscopic instrument for making examinations within a bodycavity, said instrument comprising an elongated generally cylindricalrod having an enlarged cylindrical head portion at its proximate viewingend, a cylindrical prismatic body portion at its exploratory end, and anintermediate transilluminating cylindrical rod portion, said headportion prismatic body portion and intermediate transilluminating rodportion being disposed in coaxial end-to-end relationship, said headportion presenting a planar transverse end face for viewing purposes,said prismatic body portion presenting a recessed cylindrical side faceand a concave conical end face establishing with in the prismatic bodyportion an effective internal convex reflecting conical face in radialregister with said side face, said apex region of said concave conicalendface is truncated by the provision of a cylindrical pilot socket cen=trally of said end face whereby the effective internal convex reflectingconical face likewise is similarly truncated, said side face of theprismatic body constituting a surface of light incidence whereby lightreflected from the wall of the body cavity and entering the prismaticbody through said side face will be totally reflected from saideffective convex conical reflecting surface and directed through theintermediate transilluminating rod portion to the planar end face of theenlarged head portion for emergence therefrom.

References Cited UNITED STATES PATENTS 1,791,794 2/1931 Chensney 128-3982,724,766 11/1955 Hawley et al, .0... 350-96 XR, 2,843,112 7/1958Miller,

3,224,320 12/1965 Knudsen,

'JEWELL PEDERSEN, Primary Examiner. O, B, CHEW, Assistant Examiner,

